A technical glitch caused the Web sites of both Microsoft and Yahoo! to become blocked for some users over the weekend.

For around twelve hours on Saturday many visitors looking for these popular sites and others, including msn.com were instead sent to the web page of domain registration and management outfit MyDomains.com.

The problem arose because MyDomains.com release of a DNS (Domain Name System) table laden with errors. The faulty lookup table, which was published due to human error, resulted in misdirection of surfers whose ISP used the corrupted data, until the problem was fixed late on Saturday.

Microsoft spokesman Adam Sohn told news service AFXpress: "We started getting calls from users over the weekend, we tracked down the trouble and we notified MyDomains."

It's not the first time possible weaknesses with the DNS system, which matches Web addresses to IP addresses, have come to light. There are only around a dozen 'root nameservers' on the Internet and its common practice for ISPs to use other servers, which may contain less reliable data.

Corrupting locally accessed DNS servers could be used by attackers to hijack users traffic and direct them to false sites. ®